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Exhaust advise


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Hi all I have a 2005 wrx. It's got a prodrive exhaust, but as far as I know not the complete ppp (still trying to find that out) , but it was at 250bhp before I remapped it, so I guess it could be the ppp, but I have no certificate to prove it.

I've changed the panel filter to a cosworth one and had it remapped and is now at 285hp. It's my daily runner, so I'm not looking to get anymore hp as I think I'm at the max for the car, but if the exhaust needed replacing what should I go for? If I was to go up to 3" would I need to remap again? Would this push the hp to high for the gearbox etc?

Many thanks

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A remap would be recommended to maximise any gains you may get but from what I'm aware your good for about 330lbft I'm not sure maybe more , on the factory 5 speed I don't see an exhaust pushing you over that , also your tuner should be able to tune appropriately within the tolerances of the gear box

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Alot depends on mechanical sympathy. i mullered 3rd gear in my old classic at 280ftlb, but was on the mountain pass on the isle of mann hahaha, its torque that kills box's rather than bhp.

I ran my type r 5 speed at 330bhp/380ftlb but was only for about 4k miles and i knew it was being pushed so no hard launches. As said 330-350ftlb is typically as far as you'd would push a 5 speed, only exception being a hawk 5 speed, for some reason they seem to be taking alot more punishment than others. I ran 400/420 on one for about 14k miles with no problems and know a few that have been run over 450ftlb without problems.

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Sounds good to me. Mine is 285 on both bhp and torque. I'm. It looking for a 400hp car, 300 is more than enough for where I live. Most of the road around here are small A roads, mostly B roads and unclassified roads. The car is very quick for here. I can hardly use all the power now lol. But 300hp might be a way to go ;-). Anything else I could do to push it over 300?

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Thanks for all the advice. I will leave it as it is for the mo. If exhaust, turbo etc needs replacing, maybe I'll do upgrades then. I'm haven't got thousands to spend. Very happy with what I have, was just getting prepared for any changes that have to be done.

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I have a 3" turbo back decat and made 280ft-lb on a 2.0 TD04. not sure having a 2.5" would give more torque.

Yes I second that I'm not convinced a 2.5 would produce more torque on a turbo car the less back pressure, the quicker the turbo will spool quicker therefore producing more lowdown torque

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When i got my exhaust i did a lot of Google and phoning specialist and the majority recommended 2.5 over 3 inch bore piping there answer was 3 inch loses to much back pressure unless running high power ...i,m not saying 3 inch is wrong and 2.5 is rightΒ its just what i learnt,if you google it you will see thats the feeling regarding subaru,s among the gurus😎in reality theres probabley no difference your happy with 3 i,m happy with 2.5 and life goes on πŸ˜‚πŸ˜‚

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A friend of mine had a 3" unbranded exhaust on his 98 wrx and kept getting low 200flb torque figures once mapped .

Went back to 2.5 h&s cat back.... 240 flbs but did drop 7 hp to end up with 265hp instead of 272 hp with the 3" .

From what I've researched a good branded 2.5" exhaust isn't restrictive on spool untill 350hp ish and some . I think it was "engine tuner" or "Harvey (rip) did a dyno test and found that 2.5" didn't restrict hp @ just over the 400 mark .

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  • 3 months later...
44 minutes ago, wrxstandard said:

Is there any power gain difference from a 2.5' cat-back setup to a 3' inch catback?

I got the ninja 2 back box (2.5) ordered but saw this on ebay. Might have to get a 2.5 centre pipe with no res.

β–ˆ W β–ˆ R β–ˆ X β–ˆ

I doubt it since the cats are the most restrictive part... if it's decat, probably a slight power increase

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